The only thing I've used Discord for is to set up meets for Pokemon Go raids and other events. I don't find it too useful for critical discussion.
The Unspooled group on Facebook is very well-maintained, but having seen behind the hood a bit I know it takes a LOT of moderation to keep it civil. It still seems to be the main community outlet for that podcast, as the other ones just haven't taken off much. I would love for the forums to still be the main place, but participation has just been dwindling over there.